Stem Cell Therapy in the Management of Fracture Non-Union - Evaluating Cellular Mechanisms and Clinical Progress

Delayed Union and Nonunion: Current Concepts, Prevention, and Correction: A Review

Surgical management of fractures has advanced with the incorporation of advanced technology, surgical techniques, and regenerative therapies, but delayed bone healing remains a clinical challenge and the prevalence of long bone nonunion ranges from 10 to 15% of surgically managed fractures. Delayed bone healing arises from a combination of mechanical, biological, and systemic factors acting on the site of tissue remodeling, and careful consideration of each case's injury-related, patient-dependent, surgical, and mechanical risk factors is key to successful bone union. In this review, we describe the biology and biomechanics of delayed bone healing, outline the known risk factors for nonunion development, and introduce modern preventative and corrective therapies targeting fracture nonunion.

Bone Marrow Stromal Cells Sorted by Semiconducting Polymer Nanodots for Bone Repair

The use of bone marrow stromal cells (BMSCs) for bone defect repair has shown great promise due to their differentiation potential. However, isolating the BMSCs from various cell types within the bone marrow remains challenging. To tackle this issue, we utilized semiconducting polymer dots (Pdots) as markers to select the BMSCs within a specific time frame. The therapeutic efficacy of the obtained Pdot-labeled BMSCs was assessed in a bone defect model. Initially, we evaluated the binding capacity of the Pdots with four different types of cells present in the bone marrow including BMSCs, osteoblasts, macrophages, and vascular endothelial cells, in vitro. Notably, BMSCs showed the most rapid uptake of the Pdots, being labeled within only one h of coculture, while other cells took four h to become labeled. Moreover, by colocalizing the Pdots with Prrx1, Sca-1, OSX, F480, and CD105 in the bone marrow cells of monocortical tibial defect (MTD) mice in vivo, we determined the proportions of BMSCs, macrophages, and vascular endothelial cells among all labeled cells from 1 to 8 h after the Pdots injection. It was found that BMSCs have the highest proportion (92%) among all labeled cells extracted after 1 h of Pdots injection. The therapeutic efficacy of the obtained Pdots-labeled BMSCs (1 h) was assessed in a bone defect model. Results showed that the new bone accrual was significantly increased in the treatment of Pdots-labeled BMSCs compared to the bone marrow cell-treated group. Our study revealed that BMSCs screened by the Pdots could improve bone defect repair, suggesting a promising application of the Pdots in bone healing.

Transcriptome Sequencing Analysis of lncRNA and mRNA Expression Profiles in Bone Nonunion

Background

Bone nonunion is a serious complication of fracture. This study explored the differentially expressed lncRNAs (DELs) and mRNAs (DEGs) and identified potential lncRNA-mRNA interactions in bone nonunion.

Methods

We extracted total RNA from three bone nonunion and three bone union patient tissue samples. RNA sequencing was performed to detect DELs and DEGs between bone nonunion and union tissue samples. The lncRNAs and genes with absolute log2-fold change (log2FC) > 1 and adjusted p value < 0.05 were further chosen for gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. lncRNA and targeted mRNA interaction networks were constructed.

Results

We observed 179 DELs and 415 DEGs between the bone nonunion and union tissue samples. GO analysis indicated that DELs and DEGs were mainly enriched in the chondroitin sulfate proteoglycan biosynthetic process. DELs and DEGs were enriched in “ECM-receptor interaction” and “Staphylococcus aureus infection” KEGG pathways. Several potential lncRNA-mRNA interactions were also predicted.

Conclusions

This study identified bone nonunion-associated lncRNAs and mRNAs using deep sequencing that may be useful as potential biomarkers for bone nonunion.

Effects of Collagen- and Arginine-Fortified Osteokine Supplementation on Fracture Healing

Introduction

Delayed union or nonunion is an important clinical challenge for orthopedic surgeons. In addition to the main treatment algorithms, the use of nutritional supplements is increasingly common. In this study, we investigated the effects of nutritional supplements fortified with arginine and collagen on fracture healing.

Materials and methods

Twenty-four rats with femur fractures were divided into experimental and control groups. Intramedullary fixation was performed in both groups. 20 ml/kg nutritional supplement was given to the experimental group. Radiological examination was performed at third and sixth weeks, and histopathological examination was performed at the sixth week.

Results

No statistically significant difference was found between the radiological scores of the groups at the third and sixth weeks. Nutritional supplement affected the histological properties of callus. Histological evidence of bone healing was observed by the sixth week in both groups but the score was higher in nutritional supplement group. A statistically significant difference was found between the histopathological scores of the groups at the sixth week.

Conclusion

Arginine- and type two collagen-augmented traditional nutritional supplements may help to achieve more successful results in fracture healing.